Starting with Dirac [1]}[2]} and developed more fully by Hojman, Kuchař, and Teitelboim, a chief contribution of the DHKT program was the recognition that covariant dynamical theories had a rich structure that could be traced to the kinematics of surface deformations. Such structure can, however, itself be studied independently of any particular dynamics being considered. We give a brief review of the subject following the presentations of Kuchař [3]} and Teitelboim [4]}.
